Photographic enlarger

ABSTRACT

A photographic enlarger having an electronic discharge flash tube as the light source for making the exposure, there is additionally provided an auxiliary light source for permitting focusing. Color value filters and light attenuating elements in the form of polarizing material discs are also provided.

United States Patent 1 Rear-don 1 1 Feb. 13, 1973 PHOTOGRAPHIC ENLARGER[76] Inventor: Edward A. Reardon, 5183 Bohlig Rd., Los Angeles, Calif.90032 [22] Filed: July 14, 1970 [21] App1.No.: 54,709

[52] US. Cl. ..355/71, 240/13, 240/95, 240/4135, 240/5l.12, 355/70 [51]Int. Cl. ..G03b 27/76 [58] Field of Search ..355/70, 71, 67, 68, 69, 37;240/13, 9.5, 20, 41.35, 51.12

[56] References Cited UNITED STATES PATENTS 2,415,635 2/1947 Hopkins..240/1.3 X

W 5': so iaem \i 2,923,812 2/1960 Hauptvogel ..240/51.12 X 2,895,3787/1959 Budcle ..355/69 3,028,483 4/1962 Simmon ..240/41.35 2,263,68411/1941 Ryan ..240/9.5 3,010,362 11/1961 Smith ..250/201 PrimaryExaminer-Samuel S. Matthews Assistant Examiner-Richard L. MosesAttorneyLavine, Cantor & Reich [57] ABSTRACT A photographic enlargerhaving an electronic discharge flash tube as the light source for makingthe exposure, there is additionally provided an auxiliary light sourcefor permitting focusing. Color value filters and light attenuatingelements in the form of polarizing material discs are also provided.

13 Claims, 3 Drawing Figures PATENTEDFE-B 1 m 3.718.298

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' nwmioa EDWARD A. REARDON ATTORNEYS PnoTooRAPnrc ENLARGER BACKGROUND OFTHE INVENTION The present invention is directed to photographicenlargement apparatus for making an enlargement from a photographicnegative.

Photographic enlargers are known which provide generally a lamp housinghaving a lamp or light source therein, a light directing reflector, anda holder for the photographic negative which is being enlarged. Thelight source or lamps used in the known photographic enlarging apparatushas been either incandescent lamps, or fluorescent lamps, or in somecases, both of these types has been provided. Such enlargers have thedeficiencies, however, of generating heat and requiring a relativelylong exposure time. The heat generated from the light source oftencauses the negative to buckle, which results in a loss of focus, andconsequently in an inferior enlargement. In addition, the heat from thelight source results in deterioration of the negative, and consequentshortening of the life thereof. Also relatively long exposure times havebeen required, and in order to avoid vibration of the enlarger duringthis relatively long exposure time, it has been the practice in the artto make the enlarger and its related supports of relatively heavy parts,to thereby avoid the vibration problem. This has, of course,unnecessarily increased the manufacturing costs of the enlarger.

In addition to the above noted deficiencies, it has been found that thatthe supply current has fluctuated, on occasion, during the exposureperiod, thereby resulting in inconsistencies in the enlargementsproduced, due to resulting variations in light intensity from theincandescent or fluorescent lamp. Further, the lenses provided as partof the enlarger have associated with them a diaphragm to control thelight intensity which reaches the negative, but in practice, utilizationof the diaphragm has necessitated operation of the enlarger at lensopenings which are other than optimum, again providing inferior results.

Among the objects of the present invention are to provide a photographicenlarger in which improper focusing due to buckling of a negative fromthe heat of the light source is eliminated. A further object of thepresent invention is to provide a photographic enlarger which will nothave a deleterious effect on negatives used therein. Still anotherobject of the present invention is the provision of a photographicenlarger having consistent light intensity for each exposure. Yetanother object of the present invention is to provide a photographicenlarger in which the lenses may be used with optimum lens opening. Astill further object of the present invention is to provide aphotographic enlarger which may be built of comparatively light weightcomponents, thereby effecting a cost reduction. Another object of thepresent invention is to provide a photographic enlarger permitting avery brief exposure time during the enlargement.

Other objects of the present invention will become apparent uponconsideration of the additional disclosure herein.

SUMMARY OF THE INVENTION A photographic enlarger is provided having asits principal light source an electronic flash tube. A parabolicreflector is provided for the electronic flash tube, over the open endof which is an optical filter which permits passage only oflight havinga color value approximating that of a fluorescent tube. There is alsoprovided a fluorescent tube, and a second filter permitting passage onlyof light which is of substantially the same color value as that emittedby incandescent lamps. In addition to a diffuser and condenser lenses,there is also provided a light attenuating means which preferably is inthe form of a pair of discs made of polarizing material, one disc beingrotatably mounted in its plane, to thereby permit variation in theamount of light passing through the two discs. Each of the tubes isunder the control of a separate switch.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view, withparts broken away, of an enlarger in accordance with the presentinvention.

FIG. 2 is a cross-sectional view taken on line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view taken on line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,wherein like or corresponding reference numerals are used to designatelike or corresponding parts throughout the several views, there is shownin FIG. 1 an enlarger generally designated 10 and comprising a baseboardor platform 11 having extending upwardly therefrom supporting tracks 12which are parallel to each other and which are cantilevered forwardly sothat the upper ends thereof generally lie over the baseboard 11. Thetracks 12 support an enlarger head 15, and in known fashion enlargerhead 15 may be secured in various selected positions on the racks 12. Ata suitable location, such as adjacent baseboard 11, there are providedswitches 13 and 14, connected to light generating tubes to behereinafter described.

Referring now to FIG. 2, the enlarger head 15 may be seen to include ahousing 16, in the upper part of which there is fastened a parabolicreflector 17 having an open end 17', reflector 17 being directedvertically downwardly, and centered on an optical axis of the enlargerhead 15. This optical axis generally coincides with the central axis ofthe enlarger head 15. Positioned within the parabolic reflector 17 is anelectronic discharge tube 18, tube 18 being supported by its leads 19substantially at the focal point of parabolic reflector l7. Leads 19 areconnected with conductors 21 which extend to a power supply 22 of knownconstruction, but generally including a condensor which, in combinationwith other known circuitry, provides an extremely short discharge timeof electronic discharge tube 18, when energized. For example, thedischarge time may be approximately l/1000th of a second. The powersupply 22 is connected with a suitable power source through switch 13.

Also mounted in the housing 16 is a mushroomshaped reflector 27 which isdirected generally downwardly, and is centered on the optical axis ofthe enlarger head 15. Reflector 27 has in the upper portion thereof acentral opening 28, the parabolic reflector 17 being mounted above themushroom-shaped reflector 27, with tube 18 adjacent the opening 28.Secured across the open end of parabolic reflector 17, as by nut andbolt fasteners 29 which engage a flange on the reflector 17, is anoptical filter 30. Filter 30 permits passage therethrough from theelectronic discharge flash tube 18 only light having a color value,i.e., a color temperature, which matches the color value of afluorescent tube, specifically the circular fluorescent tube 38 which issecured to the reflector 27 by suitable clips 32. Conductors 33 areconnected to the fluorescent tube 38, and extend to the power supply 22,which contains the normal ballast, starter and other parts ofconventional circuitry for supplying current to a fluorescent tube. Thefluorescent tube supply circuit is connected with a current sourcethrough the switch 14.

Preferably, housing 16 is of relatively light weight metal, or materialsuch as fiberglass or plastic, and is provided with an access hole, notshown, for permitting access to a power supply 22 for repair orreplacement thereof. Housing 16 terminates at an open end 34, whichrests on a ledge 35 of lower housing 36, which latter is secured inposition by means of spring clips 37. Below the ledge 35, housing 36 maybe seen to taper towards the optical axis, terminating in a cylindricalportion 39.

Secured in the upper part of cylindrical portion 39 is a filter 40 whichwill receive light from both the electronic discharge tube 18 and thefluorescent tube 38 ,and pass light having a color value substantiallythe same as that of incandescent lamp(s).

Also mounted in the cylindrical portion 39, below the filter 40 is adiffuser 42, and below diffuser 42 there are mounted a pair of discs 45and 46 of polarizing material, disc 45 being fixed and disc 46 beingrotatable in its plane. Polarizing material disc 46 is supported on anannular ledge 47 (see also FIG. 3), and has extending therefrom a handle48. Handle 48 extends through an arcuate slot 49 in the cylindricalportion 39, to permit movement thereof. An indicator scale (not shown)may be provided on cylindrical portion 39 for cooperation with handle48, to indicate the setting of disc 47. Disc 47 is oriented relative todisc 45 so that an 7 intermediate amount of light may pass therethroughin an intermediate position of handle 48. Thereby movement of handle 48in one direction will effect the passage of more light. Hence, thisstructure including the fixed disc 45 and the movable disc 46 provide anadjustable light attenuating means.

Secured to the end of the cylindrical portion 39 is a condenser lenssystem including an upper condenser lens 50 and a lower condenser lens51, carried in a housing 55. Beneath the housing 55 is a negative holder58, which receives, in conventional manner, a negative to be enlarged.Extending beneath and connected to the lens carrier 58 is a bellows 59,which may be provided at the lower end thereof with a conventional lensboard for supporting a lens, these portions not being shown in thedrawing for purposes of clarity.

in operation, a negative to be enlarged is placed in the negative holder58, and switch 14 is actuated in order to provide energization of thefluorescent tube 38. Light from tube 38 is reflected downwardlygenerally parallel to the optical axis by the reflector 27, passingthrough the filter 40, admitting light value as above noted. Focusing innormal manner is then accomplished, and switch 14 is again actuated toturn off the fluorescent tube 38. Thereupon, photographic paper uponwhich the print is to be made is placed upon the baseboard 11 inconventional manner and the enlarger lens is set to its optimum opening.Also, the light attenuating means is adjusted, if necessary, by movementof handle 48. The switch 13 is then depressed, thereby actuating orenergizing the electronic discharge tube 18, which provides, as abovenoted, a light flash of approximately l/lOOOth second duration, thelight being parallel to the optical axis since tube 18 is at the focalpoint of reflector 17.

In connection with the enlargement of some negatives, dodging orburning-in of the image may be required; and this is accomplished bymaking the exposure with the fluorescent tube 38 as the light source,rather than the electronic discharge tube 18. For an electronic flashdischarge tube 18 having a color temperature close to that of anincandescent lamp, the filter 30 is not required, if an incandescentlamp or lamps is used, the filter 40 is not required.

The enlarger of the present invention has a pair of light sources in theform of an electronic discharge tube and a fluorescent tube, both ofwhich provide little heat, thereby avoiding warpage or buckling of thenegative and deterioration thereof. The enlarger of the presentinvention, since it utilizes primarily an electronic flash tube having alight flash of very limited duration, will not be effected unduly byvibrations, and therefore the present invention enlarger can be ofrelatively light weight construction, and therefore more economical.Fluctuation in line voltage will not effect the operation of the presentenlarger, whichever of the light sources is utilized.

It will be obvious to those skilled in the art that various changes maybe made without departing from the spirit of the invention and thereforethe invention is not limited to what is shown in the drawings anddescribed in the specification but only as indicated in the appendedclaims.

lclaim:

1. A photographic enlarger comprising:

a housing,

light generating means in said housing including electronic flash tubemeans for generating a light flash of a duration of a fraction of asecond and means for generating light and having lower heat emissionthan an incandescent lamp comprising a fluorescent tube,

means for directing light from each said tube generally along saidoptical axis,

negative holding means positioned to receive light generated by saidlight generating means,

variable light attenuating means on said optical axis between said lightgenerating means and said negative holding means, and filter means fortransmitting light having color-temperature substantially the same asthat of an incandescent lamp to a negative in said negative holdingmeans.

2. The enlarger of claim 1, and means for selectively energizing eachsaid light generating means.

3. The enlarger of claim 1, said filter means comprising a filterpositioned to intercept light only from said electronic flash tube fortransmitting only light having substantially the same color value as afluorescent tube.

4. The enlarger of claim 3, said filter means further comprising afilter positioned to receive light from both said electronic flash tubeand said fluorescent tube.

5. The enlarger of claim 1, wherein said electronic flash tube is moreremote from said negative holding means than said second lightgenerating means.

6. The enlarger of claim 5, said light directing means comprising aparabolic reflector, said electronic flash tube positioned substantiallyat the focal point thereof.

7. The enlarger of claim 1, said fluorescent tube being annular and saidlight directing means comprising a reflector for each said tube.

8. The enlarger of claim 7, said reflector for said fluorescent tubebeing generally mushroom shape and having a central opening.

9. The enlarger of claim 8, said reflector for said flash tube being aparabolic reflector with its open end at said central opening of saidmushroom shaped reflector, said flash tube being substantially at thefocal point of said parabolic reflector.

10. The enlarger of claim 1, said light attenuating means comprising apair of planar elements of polarizing material disposed generallyperpendicularly to said optical axis, and means for rotating one saidelement in its plane.

11. The enlarger of claim 10, said one element being a disc, and meansfor rotating said disc.

12. The enlarger of claim 1, and light focusing means on said opticalaxis between said light generating means and said negative holdingmeans.

13. The enlarger of claim 12, and light diffusing means between saidlight generating means and said light attenuating means.

1. A photographic enlarger comprising: a housing, light generating meansin said housing including electronic flash tube means for generating alight flash of a duration of a fraction of a second and means forgenerating light and having lower heat emission than an incandescentlamp comprising a fluorescent tube, means for directing light from eachsaid tube generally along said optical axis, negative holding meanspositioned to receive light generated by said light generating means,variable light attenuating means on said optical axis between said lightgenerating means and said negative holding means, and filter means fortransmitting light having colortemperature substantially the same asthat of an incandescent lamp to a negative in said negative holdingmeans.
 1. A photographic enlarger comprising: a housing, lightgenerating means in said housing including electronic flash tube meansfor generating a light flash of a duration of a fraction of a second andmeans for generating light and having lower heat emission than anincandescent lamp comprising a fluorescent tube, means for directinglight from each said tube generally along said optical axis, negativeholding means positioned to receive light generated by said lightgenerating means, variable light attenuating means on said optical axisbetween said light generating means and said negative holding means, andfilter means for transmitting light having color-temperaturesubstantially the same as that of an incandescent lamp to a negative insaid negative holding means.
 2. The enlarger of claim 1, and means forselectively energizing each said light generating means.
 3. The enlargerof claim 1, said filter means comprising a filter positioned tointercept light only from said electronic flash tube for transmittingonly light having substantially the same color value as a fluorescenttube.
 4. The enlarger of claim 3, said filter means further comprising afilter positioned to receive light from both said electronic flash tubeand said fluorescent tube.
 5. The enlarger of claim 1, wherein saidelectronic flash tube is more remote from said negative holding meansthan said second light generating means.
 6. The enlarger of claim 5,said light directing means comprising a parabolic reflector, saidelectronic flash tube positioned substantially at the focal pointthereof.
 7. The enlarger of claim 1, said fluorescent tube being annularand said light directing means comprising a reflector for each saidtube.
 8. The enlarger of claim 7, said reflector for said fluorescenttube being generally mushroom shape and having a central opening.
 9. Theenlarger of claim 8, said reflector for said flash tube being aparabolic reflector with its open end at said central opening of saidmushroom shaped reflector, said flash tube being substantially at thefocal point of said parabolic reflector.
 10. The enlarger of claim 1,said light attenuating means comprising a pair of planar elements ofpolarizing material disposed generally perpendicularly to said opticalaxis, and means for rotating one said element in its plane.
 11. Theenlarger of claim 10, said one element being a disc, and means forrotating said disc.
 12. The enlarger of claim 1, and light focusingmeans on said optical axis between said light generating means and saidnegative holding means.
 13. The enlarger of claim 12, and lightdiffusing means between said light generating means and said lightattenuating means.